Myocardial ischemia, including myocardial infarction, has been reported to recur in 10 to 35% of patients undergoing coronary bypass surgery. If regional myocardial abnormalities are diagnosed in the reversible phase of injury, problems related to surgical technique and unbypassed lesions in coronary vessels can be recognized: hence, the importance of monitoring regional myocardial function during and immediately after revascularization. Utilizing small platinum wires implanted intramyocardially, we have obtained simultaneous measurements of myocardial oxygen tension and direct intramyocardial electrograms nontraumatically in patients who have undergone coronary bypass surgery. This monitoring system has been proven to be clinically realizable and the measurements of myocardial oxygen tension and intramyocardial electrograms have been shown to be sensitive to myocardial ischemic changes in these patients. Furthermore, recent preliminary studies in our animal laboratory suggest that the same platinum electrode system can also be used to measure regional left ventricular wall motion as well. This research proposal is an effort to develop and experimentally test a system that, utilizing only small intramyocardially implanted platinum wires, will be able to monitor regional myocardial function in patients following coronary bypass surgery by measuring myocardial oxygen tension, intramyocardial electrograms and regional wall motion. Because myocardial oxygen tension, electrograms and wall motion respond rapidly to changes in myocardial function, this monitoring system will be of vital aid in determining the efficacy of various drug therapies. In addition, the recordings of myocardial oxygen tension, electrograms and wall motion will be invaluable for describing the natural course of ischemic heart disease.